http://www.greenbuildingadvisor.com/blogs/dept/musings/radiant-barriers-solution-search-problem

No news there, really.

Even in roof/rafter applications where they're most-useful radiant barriers still underperform light-colored moderate to high-emissivity roofing ("cool roof") materials on the exterior a negligible or no extra cost in new construction. See: http://www.fsec.ucf.edu/en/publications/pdf/FSEC-PF-337-98.pdf

Moderate performance multi-foil laminates have been around awhile (there appears to be a renaissance of it going on in Europe & the UK over the past decade- have you seen the movie "Radiant Barriers Gone Wild"??? :-) ), but are way behind the alternative methods in actual performance-per-dollar (or euro.) See:

http://www.comparethemultifoil.com/

To interpret what those metric U-values mean in USA-R terms:

U0.30 is about R19

U0.25 is about R23

U0.18 is about R31

Note that even with 7 layers in conjunction with ~ 80mm ( R19) of PIR (iso) in a wall assembly most of them can't hit R31 performance. If 7+ layers can't buy you another R12, what's the point? Maybe the 19-layer stuff being touted is pretty good, but so are a lot of other (usually cheaper) construction methods & materials.

There have also been a lot of over-reaching performance claims for these products, with whining over test methodologies etc (in-situ vs. guarded hot box EN ISO 8990/ASTM C1363 style), with academic & government sponsored testing demonstrating the accuracy & correlation of EN/ASTM test methods with real-world performance.

Greetings,

QUOTE> Even in roof/rafter applications where they're most-useful radiant barriers still underperform light-colored moderate to high-emissivity roofing ("cool roof") materials on the exterior a negligible or no extra cost in new construction.

NOT TRUE. Over the existing material. What part of that don't you understand.

Which brings up the age old question, what field of the construction business are you in?

I'll take the test data from the Florida Solar Energy Cente and Lawrence Berkeley Nat'l Labs on the relative performance of cool roof (even paint-on, over existing material) vs. radiant barrier over the unsupported bald assertion of somebody selling & installing radiant barrier. YMMV ;-)

Cool roof is great for commercial applications or even certain residential ones. I am not sure if it would work for most residential applications though. There is no argument on that value of it but I am just not sure about residential applications.

Do you think that it would be difficult to justify the extra cost of a cool roof for residences?

Greetings,

QUOTE> I'll take the test data from the Florida Solar Energy Cente and Lawrence Berkeley Nat'l Labs on the relative performance of cool roof (even paint-on, over existing material) vs. radiant barrier over the unsupported bald assertion of somebody selling & installing radiant barrier. YMMV ;-)

Even though it's a poor test.
The assertion remark indicates I and others might be lying. As I have mentioned before you are not important enough to lie to. I think your ego is a bit inflated.
By the way, just what is your agenda. Since you won't reveal your assc in the construction field I have to assume you are just an arm chair expert. How sad.
It's obvious you have no direct experience with RB so isn't it a bit pompous to dis RB ?
Like I said before I don't have to insult you, you do so yourself. I just bring attention to it.

Generally speaking, these so called tests "claim" to represent installed conditions. I beg to differ.
My experience, over 30 yrs is that properly install RB will out perform, toe to toe, all other insulation materials in the, out in the real world. conditions. And I know that is is the experience of many others.
This material has proven it's self for close to 90+ yrs despite underhanded tricks by bulk insulation manufacturers and the Gov, ( God bless the USA, Inc). If RB where not as good as they are they would not be on the market.

I have brought this example up a few times and have asked our experts (?) why is it that the attic air space of a type 4 RB ( 3 layers/4 reflective air spaces,) on a 95 degree day , unshaded, black roof will only be about 11 degs above ambient? NO RESPONSE. WHY? because to answer would reveal the superior value of RB. And some one with a hidden agenda can't afford that. The method I now recommend is even more efficient although the attic temp remains the same. PLEASE, ANYBODY.

By the way the Gov post on insulation tries to steer people away from RB using the following statement , paraphrasing, RB ARE NOT AS EFFECTIVE IN THE WINTER. Compared to what. Was it a single layer of foil or multi? Were the other materials subject to condensation conditions? The list of emissivity chart makes no distinction in the foil effectiveness in any direction. Why is this ignored? Just what was the test conditions to come to that conclusion? Was it direct comparison? Inquiring minds want to know.

The labs listed are Gov controlled, state or fed. The govs makes 10's or even 100's of billions in UNEARNED tax revenue by steering you to the less efficient materials. And yes, there is documentation of that. Any time you let the gov influence your choice you're going to get S------. If you don't know that by now, then you deserve to pay outlandish energy bills and live in uncomfortable homes.

And if you think this is a hot issue just what until the ZPE and other fuel less electric generating devices start hitting the market. The Gov is already suppressing that field and has been for several decades. When these devices hit the market the home owner isn't going to care what insulation is in his ceil/walls or how many windows they have, or how big the HVAC is, BECAUSE, it isn't going to cost anything to operate except for the initial cost.

A good website to ck is: peswiki.com , they keep track as to what is going on.
Right now they are tracking a Italian "cold fusion device, (CFD) that in it's smallest form produces 27 k watts. It is being publicly shown and operated today. And there is at least one other CFD that is about to be revealed to the public. Why isn't that in the news? There has already been a push to limit or ban these devices by politicians, claiming dangerous radiation,(known or unknown). ( God bless politicians, INC)

You think you're free? Please, don't get me started.

Posted By PDArch on 06 Oct 2011 11:03 AM
Cool roof is great for commercial applications or even certain residential ones. I am not sure if it would work for most residential applications though. There is no argument on that value of it but I am just not sure about residential applications.

Cool roofs on residential buildings are now required by code in CA under Title 24.  The minimum SRI required varies by local CA climate zone and roof pitch, and there are exceptions allowed based on engineering analyses of total energy use.  (IIRC rafter mounted radiant barrier is an acceptable alternate construction, as is a calculated increase in attic or roof insulation, RB roof sheathing such as foil faced ply or OSB isn't. )

See: http://www.coolroofs.org/documents/...Update.pdf

Posted By Alton on 06 Oct 2011 01:26 PM
Do you think that it would be difficult to justify the extra cost of a cool roof for residences?

In new construction it isn't necessarily an uptick in cost, just a narrower range of color choices.  It's not rocket science- no special materials required, just a third party verified rating of solar reflectivity & emissivity.  It doesn't have to be titanium-white to work, and nano-bead additives do not appreciably improve nor harm performance.

rbisys1: I have no economic ties to the construction industry. It's not about me, it's about the verifiable facts & third party testing vs.unsupported/poorly supported claims. My degrees are in mathematics & physics ( ergo I work as a lowly engineer. :-) ) There is more credibility in test data than in unsupported assertions by those with an agenda or an economic interest. I design stuff to actually work, and am usually required to test & PROVE that is actually works before getting paid.

"If RB where not as good as they are they would not be on the market."???

Who's gonna stop 'em- the government? (Well, actually the FTC does step in to make examples of some of the most egregious claims...) Sure RB works in some applications well enough to be cost effective, not so much in others. But when looking at true high-performance building envelopes it's usually way down there on the list. As retrofit to code-min 1970s attics it's almost always a winner, but isn't necessarily the first-most cost effective thing to do to those buildings.

The FSEC strongly promotes the use of RB, but also advocates building with cool-roof materials. Their testing is not all small setup laboratory experiments, they have NUMEROUS field tests & monitoring of occupied houses- you don't get any better "installed conditions" than that. The LBL and many local CA utilities and MANY others have verified and fought over the standards for CA Title 24 to make sure that the standards actually work and are cost-effective. RB has been demonstrated to be less cost effective (as well as less-effective) than cool roofs, but are allowed as an alternative construction under Title 24.

Guarded hot-box testing has been verified as VERY reasonable metrics of in-situ performance, both in Europe and the US, and not only by government agencies.

The verifiable facts are not a government conspiracy to screw you out of your favored methods. Again you make a lot of assertions, claim to have "proof", but are not forthcoming with the same. I believe that YOU believe what you write, but I don't believe much of what you aver is supported by the facts.

Greetings,

Thank you for the resume'. I was on the verge of accusing you of being a troll. I would think you would be proud of your profession and let every one know your reasons for your position.

QUOTE> Who's gonna stop 'em- the government? (Well, actually the FTC does step in to make examples of some of the most egregious claims...)

I assume you're talking about RB. Yes and the RB manufacturers are not too happy with con artists either. They have enough problems with out con artists muddying the water more.
In 1981 the FTC made effective new rules about testing ALL insulation materials. The mineral wool cos. went to the senate and the senate closed down the FTC for 2 days until they rescinded the new rules. That is on record. The FTC like all the rest of the Gov depts are paper tigers answerable to industry.
The US Senate has interfered at least three times to cripple the RB industry.
And why just the MOST egregious claims. A thousand small pricks can kill just as much as a sword.

I kinda feel sorry ( not pity)for folks like you who put their eggs in the printed basket. If you were to build a RB house to my specs I guarantee you, you would be singing a different song.

The guarded hot box test used to attain approval is not an in situ test. It is for a limited period. Why is it engineers are so infatuated with tests? Go out and prove it for yourself.

QUOTE> The FSEC strongly promotes the use of RB, but also advocates building with cool-roof materials. Their testing is not all small setup laboratory experiments, they have NUMEROUS field tests & monitoring of occupied houses- you don't get any better "installed conditions" than that. The LBL and many local CA utilities and MANY others have verified and fought over the standards for CA Title 24 to make sure that the standards actually work and are cost-effective. RB has been demonstrated to be less cost effective (as well as less-effective) than cool roofs, but are allowed as an alternative construction
under Title 24.

I would like to critique their tests. How can you beat 2 btu/hr/sq ft? You probably have a copy of Mark's
Mech. Eng. Hand book, or similar. Go do the math. And I'm talking about multi layer above drywall, not rafters.

Aver. Haven't heard that one in a coons age. What it boils down to, as you said is that I have to go on what I have experienced and learned from scientist AND engineers.

As far as the Cal Energy Board goes they proved themselves to in bed with the FG people. Do you really think the Cal utilities are going to support insulation materials, of any sort, that will cut the AC by 50 + %? My local utility has been stabbing me in the back the whole time I've been in business. They told me to my face twice that they do not make any money on my houses. They have changed meters on at least 2 of my houses because the usage was TOO LOW.

Some times, and including me, our credentials are our own worst enemy and we are trapped by the very thing we hope to set us free. (so to speak)

Tomorrow I'll call Fi Foil and ck to see if this was more of these rafter tests. I have a feeling it was.

Posted By PDArch on 06 Oct 2011 11:03 AM
Cool roof is great for commercial applications or even certain residential ones. I am not sure if it would work for most residential applications though. There is no argument on that value of it but I am just not sure about residential applications.

I'm quite curious as to why they would not work on most residential applications? I'm not disagreeing ... I just need educating.

bpnkrtn-

I am not sure what PDArch had in mind, but I do see certain disadvantages of cool roof materials.
From what I understand, the cool roof colors are light colors only (light colors tend to reflect more solar radiation than dark colors). I had a light tan "cool roof" put on a house that I owned in Texas. These roofs presumably work properly in reducing roof and attic temperatures, which not only reduce cooling bills, but could prolong roof lifetimes since heat tends to destroy composition shingles. However, the light colors tend to show stains from trees, etc. more so than dark colored roofs. Some neighborhoods have deed restrictions that limit roofs to dark colors, and I assume that it is for that reason. Take a drive around an older neighborhood with a variety of roof colors, and see if you don't notice that the lighter roofs tend to show more discoloration and color non-uniformity than the darker roofs.

Cool roof shingles come in a range of colors, just no deep gray or black or deep red.

CA Title 24 also qualifies massive roofs (terra cotta or cementious) as cool roof materials in almost any color due to the delayed (and lower) peak temps due to the thermal mass of the material, which allows it to radiation-cool favorably after the solar-peak. It's not a very cheap roof, but most are very long-lived. There's quite a variety of standing-seam metal finishes that cut the mustard too, but also not cheap.

Deed restrictions requiring dark roofs in TX sounds like a brain-dead policy to me, no matter what it looks like.

BTW, rbisys1: " Do you really think the Cal utilities are going to support insulation materials, of any sort, that will cut the AC by 50 + %?"

The answer to that is a resounding:

YES I REALLY THINK SO- if it really worked that well, they'd be all over it!!

The regulatory climate in CA for the past 25-30 years has made paying for demonstratable ratepayer reductions in load is better for the  utilities' bottom line than increased generation.  If any RB stackup worked that well and was cost effective you BET they'd buy (or subsidize) it, since that's how they can make the most money.

But they don't require or subsidize radiant barrier except in low R buildings that don't have the requisite cool roof materials. As a rule, RB is plan-B.

And why is that? Contrary to your conspiracy notions, it's because it doesn't work nearly that well, or is uneconomic relative to alternate methods, and demonstrably so.

CA Title 24 wasn't created by the utilities, the fiber insulation industry, or the roofing materials industry, all out to screw radiant barrier vendors.  It's requirements are vetted on economic efficacy after much public discussion and no small amount of research. The level of subsidies for retrofits are determined by ongoing in-situ measurements of actual performance.  Implementing Title 24 measure does not present a long term economic burden on the buyer/ratepayer unless they go way out of their way to do it in the most-expensive way (such as 5" of closed cell polyurethane to meet an R30 min roof, etc.)